Iran will export most of its enriched uranium stockpile to Russia in the coming days as it rushes to implement a nuclear deal and secure relief from international sanctions, Tehran's nuclear chief was quoted as saying on Saturday.

Under the terms of the deal it reached in July with world powers, Iran must reduce its stockpile of enriched uranium to around 300 kilograms (660 pounds), mothball most of its centrifuges, and remove the core of a heavy-water reactor at Arak so it cannot be used to produce plutonium.

"In the next few days around nine tonnes of Iran's enriched uranium will be exported to Russia," nuclear chief Ali Akbar Salehi was quoted as saying by state news agency IRNA. That is roughly the amount that Iran must export to bring its stock down to the required level.

On Wednesday, Tehran said it was working to complete the requirements in the next two to three weeks, after the International Atomic Energy Agency closed its investigation of Iran's past nuclear activities.

IAEA chief Yukiya Amano, responsible for verifying that Tehran has taken the necessary steps, said it is "not impossible" that sanctions could be lifted in January, ahead of important Iranian elections in late February.

Iran has already received a shipment of yellowcake, an unenriched uranium compound, from Russia in exchange for the enriched uranium.